The present invention is directed to rotary cutting tool for rough or finish a concave spherical seat coaxial with a bore through a workpiece in a mass production transfer line or a similar setting. One application to which the cutting tool of the present invention is especially well adapted is that of cutting spherical seats on the interior of an automotive differential case.
Indexable inserts employed on rotatable cutting tools for forming concave spherical recesses in workpieces have been utilized for many years, see, for example, Mizuno et al U.S. Pat. No. 4,252,480 and Allaire et al U.S. Pat. No. 4,618,296, for example.
Indexable cutting inserts of the type with which the present invention is concerned are typically formed, as disclosed in Mizuno et al U.S. Pat. No. 4,252,480, as a flat platelike cutting element having three like convexly curved cutting edges. The insert is seated in an open pocket with two sides of the insert engaged by side walls of the pocket which is formed in the cutter body with the cutting edge of the third side of the insert projecting outwardly from the body. When one cutting edge becomes worn, the insert is removed from the pocket and rotatably indexed so that the worn cutting edge is now located against a side wall of the pocket and a fresh cutting edge projects from the body. When all three cutting edges are worn, the cutting edges may be reground to restore their sharpness or, in applications where a fair degree of precision is required, may be discarded.
In a mass production transfer line or similar environment, the ability to rapidly change or replace tooling, such as worn cutters, is of paramount concern in that the shutting down of one machine on the line completely stops the flow of parts or workpieces along the line. This requires not only that the cutters be mounted upon the cutter body in a manner such that they can be rapidly indexed to replace a dulled cutting edge with a sharp cutting edge, but also that the entire cutting tool can be rapidly replaced so that the indexing can be performed on one tool while the machine is in operation with a second tool.
The replaceable or throwaway insert when indexed or replaced does not require a resetting of the cutter body location in relation to the workpiece as is the case with the conventional brazed insert which must be reset by way of machine spindle stop adjustment.
In addition to being mounted upon the cutting body in a manner accommodating rapid indexing, the locating and maintaining of the position of the cutting insert relative to the cutting body requires a high degree of precision. This latter requirement is not always compatible with rapid tool changing or indexing.
The present invention is especially directed to solutions of the problems referred to above.